The story of social networks depending on network effects alone is the story of Wile E Coyote going off a cliff; it works and until it suddenly doesn’t. Hey, remember Digg?

Reddit’s risk here is that there’s very little value to their back catalogue, since most users use it as a stream of new and novel things. So the only thing protecting reddit is that it’s still the main place people go to post funny videos and similar, which is much easier to move than their back catalog. The fact that video playback basically doesn’t work is a serious problem here.